1. Field of the Invention
This invention relates to an implement for aerating grass covered ground and includes multiple aerator units having respective aerator shafts that are mounted to a support of the implement for up and down swinging movement parallel with horizontal as well as pivotal movement toward a position inclined relative to horizontal in order to enable each of the shafts and aerator elements carried thereon to independently follow the contour of the ground. A spring assembly and optional weights mounted on arms supporting the aerator shafts bias the aerator elements into the ground as the implement is advanced, and preferably the spring assembly has structure for causing upward swinging movement of each aerator unit to be resisted by the weight of the implement support frame whenever such unit is pivoted upwardly past a certain, predetermined elevation.
2. Description of the Prior Art
The advantages of aerators are widely known to individuals responsible for maintaining a healthy, vigorous stand of grass on golf courses, athletic fields, lawns or other areas which are sodded. In general, aerators include a plurality of earth piercing elements which penetrate the ground as the implement is advanced along the field in order to prune root growth, aerate the soil and thatch the existing turf while leaving remaining portions of the seeded areas untouched so that normal use of the turf subsequent to the aerating operation is not substantially limited.
Certain types of known larger aerators are adapted to be pulled by a towing vehicle such as a tractor, and include one or more aerator units or sections. Each of the units includes a horizontal shaft supporting a bank of freely rotatable aerator hubs, and each hub carries a plurality of each penetrating elements which extend radially outwardly relative to the shaft. As the implement is advanced across the ground, the hubs rotate and the aerator elements penetrate spaced regions of the turf to stimulate growth and improve conditions for reseeding without unnecessarily exposing the lawn to damage due to washouts or other conditions.
However, conventional multiple gang aerators are not entirely satisfactory for a number of reasons. In general, aerator units which are pivotally mounted to a frame or support of the unit permit up and down swinging movement of each unit only in such a fashion that the longitudinal axis of the shaft carrying the aerator elements is retained in a horizontal position, such that the shaft of each of the units cannot individually be tilted to more precisely follow any inclination in the contour of the ground. In addition, the aerator elements of known implements are urged toward the ground only by the influence of the mass of the respective unit and any weights carried thereon. Thus, each of the units is swingable upwardly when dense or highly compacted soil conditions are encountered, thereby causing inadequate depth of penetration of the aerator elements in regions where such aeration is most desirable.